The present invention relates to a process for producing a semiconductor device using an insulating substrate, such as a sapphire substrate.
The term sapphire is generally used in semiconductor engineering to indicate .alpha.(alpha)-Al.sub.2 O.sub.3 and is also used herein according to the same general meaning.
In the production of semiconductor devices, such as SOS (silicon on sapphire) devices using sapphire substrates, each sapphire substrate should be identified in the production steps of the semiconductor devices, such as an epitaxial growth step or oxidation step of a silicon layer. Identification has previously been performed by engraving a mark, such as numerals, on the sapphire substrates using, for example, a diamond tool. Since sapphire has a low resistance to rapid heating and cooling, the sapphire substrates are liable to crack if they are rapidly heated or cooled. In the production of the semiconductor devices, the sapphire substrates are, therefore, slowly heated to, for example, the epitaxial growth temperature and slowly cooled from such a temperature, so as to prevent cracking of the sapphire substrates. Although the sapphire substrates are carefully heated and cooled in the production of the semiconductor devices, cracking frequently occurs due to the grooves of the identification mark.
Since it is difficult and expensive to identify the conventional identification marks by an optical instrument, the identification of the sapphire substrates has conventionally been manually performed, which is a disadvantage of the conventional marking process.
The conventional process for forming semiconductor elements in a semiconductor layer, which is formed on an insulating substrate, such as in an SOS structure, is complicated and control of the process is difficult due to manual marking.